THE PHENOMENON of monocular diplopia (or binocular triplopia) which is observed in some patients with concomitant strabismus consists essentially of the simultaneous localization of a single physical stimulus, reaching one eye, in two different subjective visual directions, one normal and one abnormal. As a consequence, patients who display this phenomenon have triplopia when observing with both eyes.
Binocular triplopia is rare as a spontaneous occurrence.1 This is not surprising in view of the special conditions required for its appearance. Modern investigations with major amblyoscopes of patients with concomitant strabismus have shown, however, that one can relatively frequently elicit it artificially (Cass2). Indeed, Walraven3 has developed a special orthoptic technique for the treatment of anomalous correspondence which utilizes monocular diplopia as a starting point. The interest in this fascinating phenomenon has, therefore, increased considerably of late; it has been taken out of the realm of purely academic problems,